QDFS.lua

--[[
@title QDFS
@chdk_version 1.7

#coc = 15 "CoC (um)" [5 30]
#brak = 0 "X bracket mode?" {ISO Tv}
#isoval = 0 "X Bracketing Value" {Canon ETR+1Ev ETR+2Ev ETR+3Ev ETR+4Ev ETR+5Ev}
#sleep_time = 0 "Delay (s)" [0 10]
#dis = 1 "Display" {#Bracks Focus}
#lensmag = 0 "Get Mag" {Off On Dynamic}
#reg = 1 "H/x Reg Dis" [1 3]
#offset = 1 "Console offset" [1 12]
#title = 1 "Title Line" {Off Full Exit}

Notes: 
*
* This Quasi Depth of Field Scale script only runs on the M3 with the XIMR version of CHDK, ie CHDK 1.7
* 
* The script provides visual feedback for manual deep focus bracketing, ie not for macro focus bracketing
* It also provides two exposure bracket options from an ETTR exposure (ISO or Tv) and one from whatever Canon AEB is set
* The script first tests to see if a Canon AEB is set. If not the script then looks at the ISO/Tv ETTR bracketing options. Canon meaning whatever AEB is set on the Canon side, or not
* Repeatedly pressing the INFO button will cycle through the Canon screens, including the Canon histogram, which will be active via touch. 
* Here you can change the AEB for example
* The script was mainly written for wide angle lenses and specifically the EF-M 11-22mm ;-)
* Only/all EF-M lenses can be used
* An estimate of the front principal location can be found from subtracting the QDFS MFD from the Canon reported MFD
* Changing focal length will reset the DoF scale
* Switching out of ALT mode will exit the script
* Switching the console on in the script's menu will provide additional feedback, eg the lens stepper count and the Canon lower and upper focus bounds
* If you are focused beyond the hypefocal, the DoF Scale will display the infinity blur in microms (on the right of the DoF scale)
* The infinity blur info will disappear if you focus beyond the Canon 'data infinity', when additional info will be shown
* If selected, the number of brackets to the hyperfocal is also shown on the right, as you focus short of H/3
* If Focus is selected in the Display menu, then an ESTIMATE of the focus distance from the sensor is displayed: this can be compared to the Canon reported distance
* and the mag tuned as required
* Pressing the MENU button in ALT mode will toggle the bar on and off, eg as an aid to composing
* Pressing the RIGHT button will ETTR, and pushing the LEFT button will ETTL. ETTR and ETTL thresholds can be changed in the code.
* If things don't look right either change focal length to reset things or restart the script or the camera ;-)
* Further info on the script may be found on my blog, including dynamic focus calibration when the script is running

Release 1.3351
photography.grayheron.net
January 2023
--]] 

bi = get_buildinfo()
require "drawings"
props=require'propcase'
capmode = require("capmode")
set_exit_key("down") -- change as required

tg = 242
bar = draw.add("rectf", 0, 0, 0, 0, tg,tg)
ndof = draw.add("rectf", 0, 0, 0, 0, tg,tg)
fdof = draw.add("rectf", 0, 0, 0, 0, tg,tg)
lastdof = draw.add("rectf", 0, 0, 0, 0, tg,tg)
line = draw.add("rectf", 0, 0, 0, 0, tg,tg)
hpos = draw.add("line", 0, 0, 0, 0, tg)
h3pos = draw.add("line", 0, 0, 0, 0, tg)
h5pos = draw.add("line", 0, 0, 0, 0, tg)
h7pos = draw.add("line", 0, 0, 0, 0, tg)
h9pos = draw.add("line", 0, 0, 0, 0, tg)
h10pos = draw.add("line", 0, 0, 0, 0, tg)
h0pos = draw.add("line", 0, 0, 0, 0, tg)
blur = draw.add("string",0,0,"",tg,tg)
nb = draw.add("string",0,0,"",tg,tg)
fp = draw.add("elpsf", 1, 1, 1, 1, tg, tg)
inf = draw.add("line", 0, 0, 0, 0, tg)
bar2 = draw.add("rectf", 0, 0, 0, 0, tg,tg)
cal = draw.add("string",0,0,"",tg,tg)
dot1 = draw.add("elpsf", 1, 1, 1, 1, tg, tg)
show = true
ettlmode = 0

set_console_autoredraw(1)
set_console_layout(0,0,45,3)

base_s = get_prop(props.USER_TV)
base_av = get_prop(props.USER_AV)
base_iso = get_iso_mode()
set_iso_mode(base_iso)

reset_lens = false

-- Check a few things first

if (bi.platform=="m3") and (bi.platsub=="101a") then
    FocusSearchFar_FW = 0xfc43dfd9
    FocusSearchNear_FW = 0xfc43dfff
    FocusPositionWithLensCom = 0xfc5a85c7
    shutter_trigger = "print"
  elseif (bi.platform=="m3") and (bi.platsub=="120f") then
    FocusSearchFar_FW = 0xfc43e349
    FocusSearchNear_FW = 0xfc43e36f
    FocusPositionWithLensCom = 0xfc5a8adf
    shutter_trigger = "print"
  elseif (bi.platform=="m3") and (bi.platsub=="121a") then
    FocusSearchFar_FW = 0xfc43e379
    FocusSearchNear_FW = 0xfc43e39f
    FocusPositionWithLensCom = 0xfc5a8b0f
    shutter_trigger = "print"
  else
    print("Only runs on the M3")
    sleep(3000)
    return -- exit
end

if get_focus_mode() ~= 1 then 
    print("Switch to manual focus mode")
    sleep(3000)
    return -- exit
end

if capmode.get_name() ~= "M" then
    print("Put camera in M mode")
    sleep(3000)
    return
end

if get_gui_screen_width() == 360 then 
    hdmi = 0 
else 
    hdmi = 60 
end

if get_iso_mode() == 0 then
    print("Switch out of auto ISO")
    sleep(3000)
    return
end

if get_iso_mode() > 1 then
    print("ISO > 100 : Press any key to continue")
    wait_click()
end

set_draw_title_line(title)

-- Functions --
  
function get_focus_distance_lower() -- returns lower focus distance in mm, but note 'accuracy' is 1cm from Canon
  local  x=-1
  if (bi.platform=="m3") and (bi.platsub=="101a") then
    x=peek(0x00244918, 2)
  elseif (bi.platform=="m3") and (bi.platsub=="120f") then
    x=peek(0x0024495C, 2)
  elseif (bi.platform=="m3") and (bi.platsub=="121a") then
    x=peek(0x0024495C, 2)
  elseif (bi.platform=="m10") then -- same address in 110d, 110f, 110g
    x=peek(0x00272018, 2)
  elseif (bi.platform=="m100") and (bi.platsub=="100a") then
    x=peek(0x001FC7FC, 2)
  else
    print('Wrong platform')
  end
  if x == -1 then return -1 else return x*10 end -- in mm
end

function get_focus_distance_upper() -- returns upper focus distance in mm, but note 'accuracy' is 1cm from Canon
    local  x=-1
    if (bi.platform=="m3") and (bi.platsub=="101a") then
      x=peek(0x00244916, 2)
    elseif (bi.platform=="m3") and (bi.platsub=="120f") then
      x=peek(0x0024495A, 2)
    elseif (bi.platform=="m3") and (bi.platsub=="121a") then
      x=peek(0x0024495A, 2)
    elseif (bi.platform=="m10") then -- same address in 110d, 110f, 110g
      x=peek(0x00272016, 2)
    elseif (bi.platform=="m100") and (bi.platsub=="100a") then
      x=peek(0x001FC7FA, 2)
    else
      print('Wrong platform')
    end
    if x == -1 then return -1 else return x*10 end
end

function lens_name() -- does what it says
    local pname = 0
    if (bi.platform=="m3") then
        if (bi.platsub == "101a") then 
            pname = 0x00244969 
        else
            pname = 0x002449ad 
        end
    elseif (bi.platform=="m10") then
        pname = 0x272065 
    elseif (bi.platform=="m100") and (bi.platsub == "100a") then
        pname = 0x1FC84E 
    end
    local len = peek(pname-1,1)
    local i = 0
    local t = {}
    while i < len do
        local c = peek(pname + i, 1)
        if c == 0 then break end
        table.insert(t, string.char(c))
        i = i + 1
    end
    local name = table.concat(t)
    return name
end

function lens_cal() -- called at the start or when focal length changes: sets lens to MFD
    local test_X = get_prop(props.USER_TV)
    wheel_right() -- check wheel is in Tv adjust mode
    sleep(500)
    reset_lens = false
    draw.clear()
    draw.replace(bar,"rectf",hdmi,0,hdmi+360,20,"black","black")
    draw.replace(cal,"string",hdmi+180-50,2,"Calibrating","white","black")
    draw.overdraw()
    local temp = 0
    if get_prop(props.USER_TV) == test_X then -- in ISO adjust mode
        wheel_left()
        click("up") -- switch from ISO to Tv adjust mode
    else
        wheel_left()
    end
    repeat
        temp = call_func_ptr(FocusPositionWithLensCom)
        call_func_ptr(FocusSearchFar_FW)
        sleep(50)
    until temp == call_func_ptr(FocusPositionWithLensCom) -- make sure we are at 'infinity'
    max_count = temp
    local inf_dis = get_focus_distance_lower()
    repeat -- to find some useful data
        call_event_proc("EFLensCom.MoveFocus", -1, 1)
        sleep(50)
    until get_focus_distance_lower() < inf_dis -- lower data infinity
    far_count = call_func_ptr(FocusPositionWithLensCom)+1
    repeat -- to find magnification near H
        call_event_proc("EFLensCom.MoveFocus", -1, 1)
        sleep(50)
    until get_focus_distance_lower() < (H/reg):int() -- move to around the hyperfocal/reg
    local h_count = call_func_ptr(FocusPositionWithLensCom)
    local h_dis = get_focus_distance_lower()
    repeat
        temp = call_func_ptr(FocusPositionWithLensCom)
        call_func_ptr(FocusSearchNear_FW)
        sleep(50)
    until temp == call_func_ptr(FocusPositionWithLensCom) -- make sure we are at MFD
    near_count = call_func_ptr(FocusPositionWithLensCom)
    focus_count = near_count - far_count
    MFD = get_focus_distance_lower()
    mfd = MFD -- will be updated later
    h_count = h_count-near_count + 1
    mag = (F*(far_count-near_count))/((far_count-near_count-h_count)*(h_dis-2*F)) -- ignores hiatus and extension at this stage, ie get's things going
    draw.clear()
end

function set_up()
    dof = get_dofinfo()
    F = fmath.new(dof.focal_length,1000) -- focal length in mm (real)
    base_av = get_prop(props.USER_AV)
    n = fmath.new(av96_to_aperture(base_av),1000) -- aperture number as a real
    H = (1000*(F*F))/(n*coc) + F -- Relative to front principal
    press("shoot_half")
    repeat sleep(10) until get_shooting()
    release("shoot_half")
    repeat sleep(10) until (not get_shooting())
end

function lens_info()
    if lens_name():sub(1,4) == "EF-M" then
        return true
    else -- lens not recognised
        return false
    end
end

function check_focus()
    dof = get_dofinfo()
    dirty = false
    local test_count = call_func_ptr(FocusPositionWithLensCom) - near_count
    repeat
        test_count = call_func_ptr(FocusPositionWithLensCom) - near_count
        sleep(10)
    until test_count == call_func_ptr(FocusPositionWithLensCom) - near_count
    local test_F = fmath.new(dof.focal_length,1000) 
    local test_n = fmath.new(av96_to_aperture(get_user_av96()),1000)
    if test_F ~= F then
        repeat
            dof = get_dofinfo()
            F = fmath.new(dof.focal_length,1000)
            sleep(500)
            dof = get_dofinfo()
            test_F = fmath.new(dof.focal_length,1000)
        until test_F == F
        grabp = false
        dirty = true
        reset_lens = true
        image = false
        F = test_F
        n = test_n
        H = 1000*(F*F)/(n*coc) + F
        draw.remove(lastdof)
    end
    if test_n ~= n then
        grabp = false
        dirty = true
        image = false
        F = test_F
        n = test_n
        H = 1000*(F*F)/(n*coc) + F
        draw.remove(lastdof)
    end
    if test_count ~= focus_count then -- update things
        dirty = true
        focus_count = test_count
    end
    if lensmag == 2 and lensm ~= -1 then 
        mag = lensm
        dirty = true
        lensm = -1
    end
end

function update()
    --if at 'infinity' and not image then
    if call_func_ptr(FocusPositionWithLensCom) >= far_count and not image then
        qq1 = (H-mfd)/(2*mfd) + 1
        qq1 = tostring(qq1:int())
        qq = " CoC:"..coc..", MFD:"..mfd:int()..", H:"..H:int()..", #:"..qq1
        draw.replace(bar2,"rectf",hdmi+pos,0,hdmi+360,20,"black","black")
        draw.replace(cal,"string",hdmi+pos+5,2,qq,"white","black")
        return
    else
        draw.remove(cal)
        draw.remove(bar2)
    end
    pos = 0
    k = 300-2*pos
    draw.replace(bar,"rectf",hdmi+pos,0,hdmi+360,20,"black","black")
    local J1 = far_count - near_count
    if focus_count >= J1 then
        u = fmath.new(810000,1)
    else
        u = (F*(J1 + J1*mag - mag*focus_count))/(mag*(J1-focus_count))
    end
    if (focus_count) <= (far_count - near_count) and not show_mag then
        if u < H then
            temp = H/u
            print("#:"..(focus_count).."/"..max_count-near_count..", L/U:"..get_focus_distance_lower().."/"..get_focus_distance_upper().."mm, H/"..(temp):tostr(1)..", "..del_ev:tostr(1).."Ev")
        else
            temp = u/H
            print("#:"..(focus_count).."/"..max_count-near_count..", L/U:"..get_focus_distance_lower().."/"..get_focus_distance_upper().."mm, "..(temp):tostr(1).."H"..", "..del_ev:tostr(1).."Ev")
        end
    elseif not show_mag then
        print("#:"..(focus_count).."/"..max_count-near_count..", >INF"..", "..del_ev:tostr(1).."Ev")
    end
    mfd = (F*(J1 + J1*mag - mag*0))/(mag*(J1-0)) -- Min focus distance relative to the front principal
    T = MFD - mfd
    T = T - F - (F*F)/(mfd-F) -- hiatus estimate at MFD
    x = F + (F*F)/(u-F) + T + u
    halfdof = (mfd*k)/H
    p = k - (mfd*k)/u
    p = p:int()
    halfdof = halfdof:int()
    pj = p
    fill = "grey_light"
    if image then 
        if p == pdof then
            fill = "yellow"
        elseif p >= (pdof-2*halfdof) and p <= (pdof+2*halfdof) then
            fill = "green"
        else
            fill = "red"
        end
    end
    if (p-halfdof) <=0 then
        draw.replace(ndof,"rectf",hdmi+pos+0,14,hdmi+pos+p,20,fill,fill)
    else
        draw.replace(ndof,"rectf",hdmi+pos+p-halfdof,14,hdmi+pos+p,20,fill,fill)
    end
    if u:int() > H:int() then
        draw.replace(fdof,"rectf",hdmi+pos+p,14,hdmi+k,20,fill,fill)
    else
        draw.replace(fdof,"rectf",hdmi+pos+p,14,hdmi+pos+p+halfdof,20,fill,fill)
    end
    draw.replace(line,"rectf", hdmi+pos,10,hdmi+k,10,"white","white")
    draw.replace(fp,"elpsf", hdmi+pos+p,17,2,2,"black","black")
    local h1 = H:int() 
    draw.replace(h0pos,"line",hdmi+pos+0,0,hdmi+pos+0,20,"white")
    p = (k - (mfd*k)/(H)):int()
    if p >=0 then draw.replace(hpos,"line",hdmi+pos+p,0,hdmi+pos+p,20,"red") else draw.remove(hpos) end
    p = (k - (mfd*k)/((H/2))):int()
    if p >= 0 then draw.replace(h3pos,"line",hdmi+pos+p,3,hdmi+pos+p,17,"white") else draw.remove(h3pos) end
    p = (k - (mfd*k)/((H/4))):int()
    if p >= 0 then draw.replace(h5pos,"line",hdmi+pos+p,3,hdmi+pos+p,17,"white") else draw.remove(h5pos) end
    p = (k - (mfd*k)/((H/8))):int()
    if p >= 0 then draw.replace(h7pos,"line",hdmi+pos+p,3,hdmi+pos+p,17,"white") else draw.remove(h7pos) end
    p = (k - (mfd*k)/((H/16))):int()
    if p >= 0 then draw.replace(h9pos,"line",hdmi+pos+p,3,hdmi+pos+p,17,"white") else draw.remove(h9pos) end
    p = (k - (mfd*k)/((H/32))):int()
    if p >= 0 then draw.replace(h10pos,"line",hdmi+pos+p,3,hdmi+pos+p,17,"white") else draw.remove(h10pos) end
    p = k
    draw.replace(inf,"line",hdmi+pos+p,0,hdmi+pos+p,20,"white")
    local qq = 0
    if dis == 1 then
        qq = x:int().."mm"
        draw.replace(blur,"string",hdmi+k+10,2,qq,"white","black")
    elseif u:int() <= (H/3):int() and u:int() > 0 and dis == 0 then
        qq = (H-u)/(2*u) + 1
        qq = "#"..tostring(qq:int())
        draw.replace(blur,"string",hdmi+k+10,2,qq,"white","black")
    end
    if u:int() >= H:int() then
        qq = (1/2+((coc*H)/u)):int()
        if qq >= 0 then
            qq = tostring(qq).."um "
            draw.replace(blur,"string",hdmi+k+10,2,qq,"white","black")
        else
            draw.remove(blur)
        end
    end
end

function check_overlaps()
    if get_gui_screen_width() == 360 then 
        hdmi = 0 
    else 
        hdmi = 60 
    end
  
    if grabp and image then 
        if u:int() > H:int() then
            draw.replace(lastdof,"rectf",hdmi+pos+pdof-halfdof,0,hdmi+k,6,"grey_light","grey_light")
        else
            draw.replace(lastdof,"rectf",hdmi+pos+pdof-halfdof,0,hdmi+pos+pdof+halfdof,6,"grey_light","grey_light")
        end
        grabp = false
    end

    dirty = false
end

function myshoot()
    local prevcnt = hook_shoot.count()
    local rawprevcnt = hook_raw.count()
    press 'shoot_full_only'
    repeat sleep(10) until prevcnt ~= hook_shoot.count()
    release 'shoot_full_only'
    repeat sleep(10) until rawprevcnt ~= hook_raw.count()
end

function snap() -- single image capture
    press("shoot_half")
    repeat sleep(10) until (get_shooting())
    myshoot()
    release("shoot_half")
    repeat sleep(10) until (not get_shooting())
end

function take_bracket()
    if brak == 0 then
        local iso = get_iso_mode()
        set_iso_mode(iso)
        sleep(100)
        snap()
        local isov = iso
        isov = isov + isoval*3
        if isov > 16 then isov = 16 end
        set_iso_mode(isov)
        sleep(100)
        snap()
        set_iso_mode(iso)
    else
        local s = get_prop(props.TV)
        snap()
        set_tv96_direct(s - 96 * isoval)
        snap()
    end
end

function set_ETTR()
    do 
        local histo={}
        local total = 0
        histo,total=get_live_histo()
        local total_count = total
        total = 0
        local max = #histo - 1
        start = 230 -- top 1/3 stop
        for i = start,max,1 do total = total + histo[i] end -- get the total count in the requested bins
        local sl = 50
        if (100*total)/total_count < 1 then
            repeat
                wheel_left()
                sleep(sl)
                histo,total=get_live_histo()
                total_count = total
                total = 0
                for i = start,max,1 do total = total + histo[i] end 
            until (100*total)/total_count >= 1 or get_prop(props.USER_TV) <= -480
        elseif (100*total)/total_count > 1 then 
            repeat
                wheel_right()
                sleep(sl)
                histo,total=get_live_histo()
                total_count = total
                total = 0
                for i = start,max,1 do total = total + histo[i] end
            until (1000*total)/total_count <= 1 or get_prop(props.USER_TV) >= 1052
        end
        return
    end
end

function set_ETTL()
    do 
        local histo={}
        local total = 0
        local sl = 100
        local test_X = get_prop(props.USER_TV)
        if ettlmode == 1 then
            local isov = get_iso_mode()
            local i = 0
            histo,total=get_live_histo()
            local total_count = total
            total = 0
            for i = 0,25,1 do total = total + histo[i] end -- get the total count in the requested bins (see https://scantips.com/lights/gamma3.html)
            if (100*total)/total_count > 10 then 
                repeat
                    wheel_right()
                    isov = get_iso_mode()
                    if isov > 16 then isov = 16 end
                    set_iso_mode(isov)
                    sleep(sl)
                    histo,total=get_live_histo()
                    total_count = total
                    total = 0
                    for i = 0,25,1 do total = total + histo[i] end 
                until (100*total)/total_count <= 10 or get_prop(props.USER_TV) <= -480 or isov >= 16
                click("up")
            end
        else
            histo,total=get_live_histo()
            local total_count = total
            total = 0
            for i = 0,25,1 do total = total + histo[i] end -- get the total count in the requested bins (see https://scantips.com/lights/gamma3.html)
            if (100*total)/total_count > 10 then 
                repeat
                    wheel_left()
                    histo,total=get_live_histo()
                    total_count = total
                    total = 0
                    for i = 0,25,1 do total = total + histo[i] end 
                until (100*total)/total_count <= 10 or get_prop(props.USER_TV) <= -480
            elseif (100*total)/total_count < 10 then 
                repeat
                    wheel_right()
                    sleep(sl)
                    histo,total=get_live_histo()
                    total_count = total
                    total = 0
                    for i = 0,25,1  do total = total + histo[i] end
                until (100*total)/total_count >= 10 or get_prop(props.USER_TV) >= 1052
            end
        end
        return
    end
end

function check_X()
    del_ev = -(fmath.new(get_prop(props.USER_TV),96)-fmath.new(s,96))
    if del_ev ~= 0 then dirty = true end
    return
end

function check_buttons_etc()
    wait_click(50) -- check for a button press
    show_mag = false
    if is_key("set") and (lensmag == 1 or lensmag == 2) then
        lensm = (F*(far_count-near_count))/((far_count-near_count-focus_count)*(get_focus_distance_lower() - (MFD-mfd) - F))
        if lensmag == 2 then 
            mag = lensm 
        elseif lensmag == 1 then 
            print("Tuning Mag = "..lensm:tostr(4))
            sleep(3000)
            show_mag = true
        end
        image = false
        grabp = false
        dirty = true
        draw.remove(lastdof)
    elseif is_key("up") then -- move console position
        offset = offset + 1
        if offset == 13 then offset = 0 end
        if offset == 0 then -- then switch off console display
            set_console_layout(0,0,1,0)
            print("")
            set_console_autoredraw(-1)
        else
            set_console_autoredraw(1)
            set_console_layout(0,offset-1,45,offset)
        end
    elseif is_key("zoom_out") then -- toggle CHDK histogram on and off
        if get_config_value(1060) == 0 then set_config_value(1060,1) else set_config_value(1060,0) end
    elseif is_key("right") then -- ETTR requested
        set_ETTR()
    elseif is_key("left") then -- ETTL requested
        set_ETTL()
    elseif is_key(shutter_trigger) then
        sleep(sleep_time*1000)
        if isoval > 0 and get_prop(props.BRACKET_MODE) == 0 then
            take_bracket()
        else
            snap()
        end
        last_count = focus_count
        image = true
        dirty = true
        grabp = true 
        pdof = pj
    elseif is_key("menu") then 
        if show then
            draw_clear()
            show = false
        elseif not show then
            draw.overdraw()
            show = true
        end
    elseif is_key("display") then 
        click("display")
    end
    if ecnt ~= get_exp_count() and not is_key(shutter_trigger) then
        ecnt = get_exp_count()
        last_count = focus_count
        image = true
        dirty = true
        grabp = true 
        pdof = pj
    end
    if is_key("zoom_in") then
        last_count = focus_count
        image = true
        dirty = true
        grabp = true 
        pdof = pj
        s = get_prop(props.USER_TV)
    end
end

-- Main Section --

if lens_info() == false then -- then don't use
    print("Lens not recognised")
    sleep(3000)
    return
end

show = true
grabp = false
set_up()
lens_cal()
lensm = -1

last_count = call_func_ptr(FocusPositionWithLensCom) - near_count
focus_count = last_count
if last_count ~= 0 or (mag*100):int() <= 0 then
    print("Calibration failed: Try Again!")
    sleep(3000)
    return
end

s = get_prop(props.USER_TV)
base_s = s
del_ev = 0

if offset == 0 then -- then switch off console display
    set_console_layout(0,0,1,0)
    print("")
    set_console_autoredraw(-1)
else
    set_console_autoredraw(1)
    set_console_layout(0,offset-1,45,offset)
end

finish = false
image = false
ecnt = get_exp_count()
repeat -- stay here
    if get_alt_mode() then
        check_focus()  
        check_buttons_etc()
        check_X()
        if reset_lens then lens_cal() end -- focal length changed so recalibrate lens
        if dirty and show then 
            check_overlaps()
            update() 
            draw.overdraw()
            dirty = false
        end
    elseif not get_alt_mode() then
        finish = true
    end
    sleep(100) -- adjust as required
    if screen_needs_refresh() then dirty = true end
until finish  -- exit script